Power electronic equipment consists of various typesPower electronic circuitAssembly.It is used for transformation and control of high-power electric energy.Also called converter.It includes rectifier, inverter, DC converter, AC converter, various power supplies and switches, motor speed regulating device, DCtransmissionDevice, induction heating deviceReactive compensation deviceElectroplating electrolysis device, household appliance converter, etc.
Chinese name
Power electronic device
Foreign name
power electronic equipment
Classification
device
Alias
Converter
Composition
Various power electronic circuits
Applicable
Transformation and control of high-power electric energy
Power electronic equipment consists of various typesPower electronic circuitAssembly.It is used for transformation and control of high-power electric energy.Also called converter.It includes rectifier, inverter, DC converter, AC converter, various power supplies and switches, motor speed regulating device, DCtransmissionDevice, induction heating deviceReactive compensation deviceElectroplating electrolysis device, household appliance converter, etc.
Among them, the DC power supply can be controlled by the rectifier orDC converterComposition forDC motor speed regulation, charging (standby charging power supply), electroplating and scientific instruments.AC power can be supplied by frequency converter (seeAC conversion circuit）Composition.It is divided into variable frequency and variable voltage power supply (for AC cage typeasynchronous motorSpeed regulation), constant frequency and constant voltage power supply (used to form AC uninterruptible power supply)AC regulated power supply、Medium frequency induction heating power supply(Power output frequency up to 8 kHz for induction heating and quenching)High frequency heating power supply(The power output frequency is higher than 8 kHz for quenching and welding), etc.utilizePower electronic devicesIts fast switching performance can form a static contactless high-power switch, replacing the traditional electromagnetic contactless high-power switch.
Device protection
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Power electronic devices are affected by the performance of the devices used, and have poor ability to withstand overvoltage and overcurrent.For example, motors, transformers, etc. can normally operate for several seconds or minutes at several times of the rated current, while power electronic devices can be damaged in 0.1 seconds or less under the same conditions.Therefore, in addition to reasonably selecting the voltage and current capacity of devices when designing power electronic devices, some special protective measures should be taken to prevent the devices in the device from being damaged due to overcurrent and overvoltage.Some power electronic devices have special requirements for environmental conditions (such as temperature, cooling water pressure, wind speed, etc.), which need to be monitored to ensure reliable operation of devices.
Overcurrent protection
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Overcurrent will make the device rise rapidly. If the overcurrent is not cut off or limited in time, the device will be damaged quickly.The greater the overcurrent, the shorter the time that the device can withstand the overcurrent.Common over-current protection measures include: ① adopting fast fuse.Its fusing time is usually within 20 ms.butQuick fuseThe price is high and replacement is troublesome. It is often used as the last measure for various overcurrent protection measures. ②Set the AC circuit breaker.Its action time is longer, 0.1~0.2 seconds.It is mainly used to cut off the connection between AC circuit and AC power supply to prevent the overcurrent from further expanding. ③Install the fast DC switch.Its action time is about 10~20 milliseconds, which can protect thyristor and other components without fusing the fast fuse.Installed at the DC end of the AC circuit, used for large and medium capacity power electronic devices. ④Add fast circuit breaker.Its action time is about 2-3 milliseconds.When over-current occurs, it makes the power transformer short circuit directly through the fast circuit breaker to prevent the over-current from entering the power electronic device again. ⑤Electronic circuit is used for overcurrent detection and protection.
Overvoltage protection
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Overvoltage will damage the insulation of the device and make it unable to work.Common overvoltage protection measures include: ① adopting resistance capacitance absorption circuit.It is composed of a capacitor and a resistance in series. The capacitor is used to absorb the overvoltage in the peak state, and the resistance in series with the capacitor is used to consume the energy of the overvoltage, so as to suppress the oscillation of the circuit. ②Nonlinear resistance devices shall be selected.The over-voltage protection of power electronic devices is realized by using the characteristics of such devices that are close to the volt ampere characteristics of voltage stabilizing tubes and can be automatically recovered after breakdown.Common devices include selenium stack overvoltage suppressor and varistor. ③Electronic circuit is used for overvoltage detection and protection.
Anti interference technology
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Power electronic device is a high-power power conversion equipment, and its installation and use site inevitably has serious electromagnetic interference.The strong interference signal entering the device not only directly causes the power electronic devices to malfunction, but also mainly interferes with the control circuit of the device, causing the device to malfunction.Common anti-interference technical measures include: ① Suppress the intensity of interference signal.E.g. AC relayAC contactorThe contact is connected in parallel with the capacitor, which can reduce the electric spark interference when the contact is on or off. ②Reasonable wiring shall be made to reduce the distributed capacitance, distributed inductance and mutual inductance between conductors and prevent interference signals from entering. ③Implement electromagnetic shielding. ④The grounding point shall be correctly selected and well grounded. ⑤Strengthen the anti-interference ability of the circuit itself.Electronic components with good anti-interference performance shall be selected during design. ⑥Common control circuitDC regulated power supplyEach part of the circuit shall be led separately. ⑦The input and output impedance of each unit circuit shall be reduced as far as possible under the condition of allowable signal strength. ⑧useTransformer couplingAnd other isolation means to isolate the control circuit from the signal source or the control circuit from the main circuit of the power electronic device on the circuit to prevent interference signals from entering.
application
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Power system is the main carrier of energy utilization, transmission and distribution, and plays an important role in social economy.Fossil energyThe crisis of climate and environment makes the power system transform from large-scale development to sustainable development and intelligence.Distributed power supplyLarge scale access to energy storage devices, cooperation between local power grids, microgrids and backbone power grids, efficient and flexible transmission methods, intelligent two-way interaction between power distribution and power consumption, and improvement of power supply quality and reliability are the characteristics of power system transformation.
In the power system, the grid connected generation of renewable energy, power conversion of energy storage devices, flexible interconnection of AC and DC power grids, two-way flow of power distribution, and dynamic compensation of reactive power and harmonic need to rely on power electronic devices.With the development of high-voltage and high-power power electronic devices, the improvement of modularization, modularization and intelligence of converters, and the improvement of control strategy and modulation strategy performance, power electronic devices will play a greater role in the power system[1]。
